This project is to examine the mechanisms of cell recognition, utilizing three models: (1) mouse immunocompetent lymphocytes of thymus origin interacting with alloantigens, (2) human PBL interacting with neoantigens exposed on autologous lymphoblasts, and (3) mouse lymphoid cells and crustacean amoebocytes interacting with lipid A of LPS. BIBLIOGRAPHIC REFERENCES: Chauvenet, P. H., & R.T. Smith: Serological and cell-mediated responses between C57B1/6H and H(z1). Fed. Proc. 35:#3, March 1976 (abstract). Dyminski, J. W., & Smith, R. T.: Nature of the B cell helper activity in mixed lymphocyte reactions between immunocompetent mouse thymus cells. Fed. Proc. 35:3, March 1976 (abstract).